The invention relates to a brake system for a motor vehicle for braking individual or multiple wheels. Such brake systems typically include a hydraulic master cylinder which is actuated by a brake pedal and which is connected to hydraulically operated brakes on either side of the vehicle by means of an electrically operated valve arrangement. Furthermore, such a brake system typically includes an electrical switching device through which the valve arrangement can be controlled in order to selectively connect the master cylinder with the brakes of both vehicle sides, or either at least one brake of the right side of the vehicle, or at least one brake of the left side of the vehicle.
In order to make it easier to negotiate tight turns, it is known practice from published European patent Application 0 084 687, in particular on agricultural vehicles such as agricultural tractors, to provide two brake pedals which can be actuated independently of each other, and brake pedal having a separate master cylinder coupled thereto, for generating the necessary brake pressure for the left or the right service brakes during braking. If only one brake pedal is depressed, only the associated left or right vehicle wheels are braked, resulting in a smaller turning radii. For normal vehicle operation the two brake pedals are mechanically connected to each other by a locking device, so that even if only one brake pedal is actuated, the wheels on both sides of the vehicle are braked. Because of the connection of two brake pedals, the locking device and the two master cylinders, this known brake system requires relatively many costly components and is expensive. Furthermore, the operation of the locking device is awkward and time consuming. If the operator accidentally fails to lock the two pedals during operation on the street, operation of a single pedal can produce dangerous driving conditions.
A brake system including only one brake pedal and only one master cylinder has become known from published German Patent Application 2052401. The hydraulic connection between the master cylinder and the brakes of the left or the right wheels is controlled by an electromagnetically operated selector valve. The foot plate of the brake pedal can be pivoted from a central position to both sides about an axis in the longitudinal direction of the pedal lever. Electrical contacts are arranged on both sides of the foot plate that separate the brakes on the one side or the other side of the vehicle from the master cylinder by means of the selector valve in each case when the foot plate is pivoted. The operation of the brake pedal, however, requires some dexterity on the part of the operator. Furthermore, the possibility cannot be excluded that during a full application of the brake or in emergency braking, the brake pedal may be accidentally pivoted, so that only one side of the vehicle is braked, resulting in a dangerous situation.